The Furman (and the others as they're basically copies of the Furman anyway) has a preamp built into it as well, which gives about 20-25db of gain before whatever you put it in front of IF you use the LOW level ins and outs, if you use the HI level ins and outs, you bypass the preamp section and it's just an EQ, the LOW level ins and outs are what all the LA guys used without any OD pedals, so you may not need both OD pedals...the real problem with the Furman is it sounds like a fish fry when you use it like this, way too much hiss, so a noise gate is needed right after it. The TC one is supposed to be silent but I have no experience with it. Signal level will be fine before any pedal, not any different than running the pedal in an amp loop.